1. Field of the Invention
The invention relates to a device for determining the position and direction of sewage system channel inlets and channel outlets which lead into or out of sewer manholes in a horizontal plane.
2. The Prior Art
In practice, sewer manholes are not generally measured exactly since hitherto either no suitable systems have been available for providing information about the position and direction of the channels leading into and out of sewer manholes sewer manholes are sewage systems or it has been disproportionately difficult to determine horizontal directions of inlets are of channels branching off a manhole in a horizontal direction. For that reason, only the position and height of a sewer manhole cover are measured, and the approximate depth of the bottom of the sewer manhole and of the channel inlets and channel outlets are measured approximately with a yard stick or carpenter's gage.
This problem is dealt with by DE 33 40 317 A1 which describes a measuring device for simultaneously defining the position and height of points within cavities, especially in sewage systems, which are difficult to access. The disclosed measuring device consists of a prism staff with two reflective prisms mounted in corresponding frames. The length of the prism staff can be varied by plug-in connections of aluminum tubes of rectangular profile and different lengths and the staff can be rotated at the plug joints about its longitudinal axis. A point is arranged at the lower end of the staff for placing the staff upon the bottom of a sewer manhole or upon the bottom of a connecting channel. By measuring the horizontal angle, the vertical angle and the oblique distance to the two reflective mirrors on the prism staff, the position of the channel inlet can be calculated by mathematical methods. Its disadvantage resides in the fact that only the position of the channel inlet and channel outlet can be determined with the measuring device; but it is not possible to determine the direction of the channel into or out of the manhole.
DE 38 04 875 A1 discloses measuring and calibrating with electro-optical tachymeters in which a portable reflector of the tachymeter is mounted on a perpendicular staff. The length of the perpendicular staff may be changed steplessly. For measuring pipe conduit parts in construction trenches or shafts, the tip of the perpendicular staff is placed upon the point to be measured, and the perpendicular staff is precisely positioned vertically. The vertical positioning of the perpendicular staff is very complicated and to obtain a precise measurement, the perpendicular staff must be maintained motionless by its user for an extended period of time. For improving the manipulation of such a perpendicular staff, DE 197 11 995 A1 discloses a perpendicular staff at the handle and upper end of which there is provided a reflector of a tachymeter with a perpendicular staff holder extending at a right angle therefrom. The perpendicular staff holder consists of a perpendicular staff extension, a handle and a fastening device. The fastening device is structured as a clamp. A level slide is arranged on the extension of the perpendicular staff, which can be freely positioned and which is provided with a large level for readability even from a larger distance. While this arrangement improves the handling problem of the perpendicular staff, it is only the position, but not the direction, of channel inlets and outlets which can be determined by this perpendicular staff. It is, however, the planning measurements and conduit documentation which are required for preventing damage as a result of subsequent construction work.
Reference is also to be made to DE 296 03 681 U1 and DE-OS 1 623 111 which respectively disclose an optical plumb line for geodesic apparatus and a method and apparatus for measuring cavities, in particular subterranean caverns. These arrangements can also not measure the direction of channel inlets and outlets.